Modern hair coloring techniques involve applying one or more formulations, such as a liquid, gel, paste or cream, containing one or more dyeing agents to the hair. The dyeing agents are left on the hair for a period of time, hereinafter referred to as the "color development period" to allow the dyeing agents to change the color of the hair. Dyeing agents useful in hair formulations include "permanent", "semipermanent", and "temporary" dyes.
Permanent dyes last through many washings and generally remain until the hair grows out. The most common type of permanent dye used today are oxidation dyes. When oxidation dyes are used, one or more dye precursors are combined with an oxidizing agent, such as hydrogen peroxide, before being applied to the hair. The dye precursors then react with the oxidizing agent to produce the dye within the hair. Because it is not desirable to produce the dye until after application on the hair, oxidation dyes are typically provided in two parts: a dye lotion containing the dye precursors, and a developer solution containing the oxidizing agent. The dye lotion and developer solution are then mixed shortly before application to the hair.
Semi-permanent dyes are generally removed from the hair after two to ten washings. Semi-permanent dyes are applied directly onto the hair, and are typically referred to as "direct dyes". In contrast to permanent dyes, semi-permanent do not use oxidizing agents to produce the dye. Direct dyes penetrate into the hair during the color development period, and slowly diffuse out of the hair when washed.
Temporary dyes, also known as color rinses, are typically removed from the hair after just one washing. These dyes, instead of penetrating into the hair as with semi-permanent dyes, deposit on the hair surface. The most common temporary hair dyes are water soluble acid dyes.
The hair dyeing formulations, in addition to containing the dyeing agents, also contain other additives to provide desirable performance properties. For example, the hair dye formulation should permit rapid diffusion of the dyeing agent into the hair. The hair dye formulation also needs to be readily rinseable after the color development period.
In addition, the rheological or flow properties of the hair dye formulation are important. For example, the hair dye formulation should be easily applied or spread onto the hair by brush or fingers to provide uniform coverage of the dyeing agents throughout the hair. Also, the hair dye formulation once applied should not drip or run off the hair during the color development period. The hair dye formulation should therefore be "shear thinning". Shear thinning means that as the formulation is subject to increasing shear, such as by applying the formulation to the hair by a brush, the viscosity of the formulation decreases. This decrease in viscosity upon shearing permits easy application of the formulation onto the hair. In addition to shear thinning, once the shear is removed, the viscosity of the hair dye formulation should recover or increase back to its original low shear rate viscosity. A rapid recovery of the viscosity prevents the hair dye composition from dripping or running after application to the hair.
In order to provide these rheological properties to hair dye formulations, rheology modifiers are added. However, a problem has been to find rheology modifiers that do not adversely react with other components in the formulation or adversely affect performance properties of the formulation. For example, in two part oxidation dye hair formulations, the developer solution typically contains hydrogen peroxide as an oxidizing agent. The hydrogen peroxide tends to react with other components added to the developer, such as a rheology modifier.
An additional problem with oxidation dye formulations has been that it is desirable to provide a dye lotion and developer solution which have low viscosities for mixing, preferably less than 5000 centipoises at low shear rates (Brookfield viscometer), but when mixed, thicken to provide the desired rheological properties.
U.S. Pat. No. 4,776,855 to Pohl, et.al, hereinafter referred to as "Pohl", discloses a two part oxidation hair dye formulation which uses as a thickener Acrysol-ICS (trademark of Rohm and Haas, presently supplied by Rohm and Haas as Aculyn 22). Acrysol-ICS is a hydrophobically modified acrylate copolymer which thickens at an aqueous pH greater than about 7. Pohl discloses adding the Acrysol-ICS to a developer solution having a pH of about 1.5 to 5.5. When the developer solution is combined with the dye lotion, the resulting hair dye formulation is thickened because the dye lotion is basic and adjusts the overall pH of the hair dye formulation to greater than 7.
However, the hair dye formulation in Pohl has several disadvantages. First, in order to maintain a low viscosity in both the dye lotion and developer solution, the Acrysol-ICS generally cannot be added to the dye lotion since the dye lotion typically has a pH greater than 7. Additionally, the dye lotion often contains cationic additives that would adversely react with Acrysol-ICS since Acrysol-ICS is anionic. Second, the rheology properties of the Pohl hair dye formulation, as detailed hereinafter, could be improved.
U.S. Pat. No. 4,079,028 to Emmons, et. al, hereinafter referred to as "Emmons", discloses certain polyurethanes. These polyurethanes are disclosed to be useful primarily in latex paints as rheology modifiers and thickeners. Emmons does not disclose the use of these polyurethanes in hair dye formulations, or disclose their use in combination with certain associating agents in hair dye formulations.
It is desirable to provide a hair dye composition which has improved shear thinning properties. It is also desirable to provide a hair dye composition which has improved resistance to dripping and running once applied to the hair. In addition, it is desirable to provide a hair dye composition where the rheology modifiers can be added to either the dye lotion or developer solution of an oxidation hair dye formulation. The present invention addresses this problem by incorporating into hair dye compositions a certain rheology modifying system.